1. Field of the Invention
The present invention relates to a noise generating device used, for example, for testing the characteristics of communications equipment and audio systems.
2. Description of the Prior Art
Testing the characteristics of communications equipment and audio systems requires a signal source capable of producing random noise having a spectrum uniformly distributed over a specified band.
In FIG. 3 is shown a prior art noise generator used as such a noise signal source, which generally comprises a digital signal processor (DSP) 11 and a D/A converter 12. The DSP 11 is a general-purpose programmable processor designed for high-speed digital processing, and into which a pseudo-random number generator 11a for generating pseudo-random numbers and a digital filter 11b for limiting the band of the pseudo-random numbers are programmed. Digital data output from the DSP 11 is converted by the D/A converter 12 into an analog signal and output on line 13 for noise.
One particular drawback associated with the above prior art noise generator is that the equipment is expensive in construction since it requires the provision of the versatile but expensive DSP 11 and the D/A converter 12 for converting the digital data output from the DSP 11 into an analog signal.
In view of the above problem, there is a strong need in the art for a noise generating device which can be implemented using an inexpensive hardware configuration comprising a pseudo-random number generator constructed from a shift register, etc. and an analog filter.
Accordingly, the present invention overcomes the aforementioned short comings of the above known and similar device and methods for generating noise. The present invention is summarized and described in detail below.